Integrating molecular design and crystal engineering approaches in non-humidified intermediate-temperature proton conductors based on a Dawson-type polyoxometalate and poly(ethylene glycol) derivatives
Integrating molecular design and crystal engineering approaches in non-humidified intermediate-temperature proton conductors based on a Dawson-type polyoxometalate and poly(ethylene glycol) derivatives
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基于Dawson型聚氧乙烯酸酯和聚乙二醇衍生物的非增湿中温质子导体的分子设计和晶体工程方法的集成
DOI：
10.1039/d1nr01220g
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发表时间：
2021-04-08
期刊：
影响因子：
6.7
通讯作者：
Uchida, Sayaka
中科院分区：
文献类型：
--
作者：
Ogiwara, Naoki;Tomoda, Masahiro;Uchida, Sayaka
阴离子型金属氧簇被称为多金属氧酸盐（pom），作为质子导体的组成部分得到了广泛的研究。虽然从动力学的角度来看，在非潮湿的中温（100-250℃）条件下质子传导是有利的，但很少有固态材料，更不用说基于pom的晶体，在没有水蒸气的帮助下显示出真正有效的质子传导。在这种情况下，非挥发性质子导电聚合物被限制在基于pom的框架中，而快速质子传导是不可行的。在此，我们展示了一种在非潮湿中温条件下合成具有快速质子传导的pom -聚合物复合材料的新策略。具体来说，利用不同末端基团或链长的聚乙二醇（peg）的分子设计方法控制质子载流子密度，利用具有各向异性分子形状的大型道森型POM （[α - p2w18o62](6-)）和碱金属离子作为反阳离子的晶体工程方法精细调节作为质子载流子的约束peg的迁移率。通过整合这些方法，在150摄氏度下，质子导电性超过10(-4)S cm(-1)，与众所周知的高质子导电性固态材料相当。采用交流阻抗谱法结合比热容测量和固态核磁共振谱法讨论了质子的传导机理。
Anionic metal-oxygen clusters known as polyoxometalates (POMs) have been widely researched as components of proton conductors. While proton conduction under non-humidified intermediate-temperature (100-250 degrees C) conditions is advantageous from the viewpoint of kinetics, few solid-state materials, not to mention POM-based crystals, show truly effective proton conduction without the aid of water vapor. In this context, non-volatile proton-conductive polymers have been confined into POM-based frameworks, while fast proton conduction was infeasible. Herein, we demonstrate a new strategy to synthesize POM-polymer composites exhibiting fast proton conduction under non-humidified intermediate-temperature conditions. Specifically, a molecular design approach utilizing poly(ethylene glycol)s (PEGs) of different terminal groups or chain lengths controls the proton carrier density, and a crystal engineering approach using a large Dawson-type POM ([alpha-P2W18O62](6-)) with an anisotropic molecular shape and alkali metal ions as counter cations fine-tunes the mobility of the confined PEGs as proton carriers. By integrating these approaches, proton conductivity over 10(-4) S cm(-1) at 150 degrees C, comparable to the well-known highly proton-conductive solid-state materials, is achieved. The proton conduction mechanism is discussed with alternative current impedance spectroscopy jointly with specific heat capacity measurements and solid-state NMR spectroscopy.